Patent Document 1 discloses an ultrasonic actuator in which the raw material of a vibrating element is fabricated of a sintered alloy, and the ultrasonic actuator withstands usage in adverse environments with high temperature and high humidity, driving over long periods and the like.
However, both in this kind of ultrasonic actuator and in ordinary ultrasonic motors, a elastic body and a piezoelectric element are fixed together by adhesion. Adhesion of the elastic body to the piezoelectric element is a very important stage for the functioning of a motor. If the state of adhesion is not stable, functions of the motor are not stable, and reliability over long periods cannot be assured. In addition, issues that must be controlled to stabilize the state of adhesion are manifold: control of the amount of adhesive, control of curing conditions, and so forth. If even one of these is not stable, this will have an effect on functions of the motor.
In addition, steps of processing of a piezoelectric element to be used in an ultrasonic motor are very diverse, and because sintering steps and mechanical processing are difficult, a yield is not very good. Moreover, as mentioned above, the elastic body and the piezoelectric element are fixed by adhesion. However, because of inconsistencies in mechanical processing of piezoelectric elements, when the elastic body and the piezoelectric element are adhered, the center of the elastic body and the center of the piezoelectric element may be misaligned. If the outer diameter of the piezoelectric element protrudes outward beyond the outer diameter of the elastic body, that portion must be ground away. Hence, cracks may occur in subsequent steps, and the yield at the time of assembly may be lower.
Patent Document 1: Japanese Unexamined Patent Publication No. H8-196091